Gas turbines are equipped with a rotor body that rotates around a rotation axis, a rotor that has a plurality of blade stages that are lined up in an axial direction and fixed to the rotor body, a plurality of vane stages each of which is arranged on the upstream side of each of the plurality of blade stages, and a casing that covers the rotor and has the plurality of vane stages attached to the inner peripheral side thereof.
The structure of a casing of a gas turbine is described in the following Patent Document 1. This casing is equipped with a plurality of blade rings that form an annular shape around a rotation axis. Each blade ring covers one blade stage and a vane stage arranged on the upstream side of this blade stage. This casing further forms an annular shape around the rotation axis. Additionally, the casing is equipped with a plurality of ring segments arranged between a plurality of vane stages on the inner peripheral side of the blade rings and on the outer peripheral side of blades, and isolation rings that form an annular shape around the rotation axis and attach vanes and the ring segments to the inner peripheral side of the blade rings.
A downstream portion in an outer shroud of each of a plurality of vanes that constitute a first vane stage is attached to a blade ring for a first stage via a first isolation ring arranged on the downstream side thereof. Additionally, the ring segment arranged on the downstream side of the first vane stage has an upstream portion attached to the blade ring for a first stage via the first isolation ring and a downstream portion attached to a second isolation ring. A fixing ring as a pressing member that presses this second isolation ring to the upstream side is arranged on the downstream side of the second isolation ring. This fixing ring is fixed to a downstream end of the blade ring for a first stage with a bolt.
Elastic metal packings that are elastically deformed in the axial direction and perform sealing between both are provided between the downstream portion in the outer shroud of each of the plurality of vanes that constitute the first vane stage, and the first isolation ring, between the first isolation ring and the ring segment, and between the ring segment and the second isolation ring.